MADISON, Wis., March 16 (UPI) — U.S. scientists say they have created a simple and cost-effective technology that uses small amounts of waste energy to turn water into usable hydrogen fuel.

University of Wisconsin-Madison Assistant Professor Huifang Xu, who led the study, said his team grew nanocrystals of two common crystals — zinc oxide and barium titanate — and placed them into water. When pulsed with ultrasonic vibrations, the nanofibers flexed and catalyzed a chemical reaction to split the water molecules into hydrogen and oxygen.

The researchers explained that when the fibers bend, asymmetries in their crystal structures generate positive and negative charges and create an electrical potential. That phenomenon, called the piezoelectric effect, is well known in certain crystals and is the driving force behind quartz clocks.

Xu and his colleagues applied the same idea to nanocrystal fibers and, so far, have achieved 18 percent efficiency — higher than most experimental energy sources.

Rather than harvest the energy directly, the scientists used it to break the chemical bonds in water and produce oxygen and hydrogen gas.

Xu said the process might eventually be used to generate power from a multitude of small sources — walking could charge a cell and breezes could power streetlights.

The study that included Kuang-Sheng Hong, Hiromi Konishi and Professor Xiaochun Li is reported in the March 2 issue of the Journal of Physical Chemistry Letters.